Hey guys,

Got an issue with my ride and am at a standstill. First started with a check engine light which indicates a miss in cyl 3 and 4. Changed out dist cap, rotor, wires, and plugs and still had the light and symptoms of miss/high(1000+ rpm consistently) idle. Seems like a slight miss can be heard from the exhaust as the vehicle is running (no blue or smoky exhaust but leaves a nasty carbon build-up on my trash can) and vehicle stalls when oil cap is removed. After ~200 miles, I checked the plugs again and 3 and 4 were fouled pretty bad with an ashy build-up and possible slight oil contamination. Almost all plugs had slight oil on threads but not noticed on firing mech. and not fouled(except 3 and 4). New fuel pump, o2 sensor, PCV with no improvements.

Possible related symptom of small radiator leak/crack(unsure) which i attempted to fix with a J&B liquid stop leak. Radiator began purging the coolant system through overflow tank until i flushed the tank drain to radiator and it seemed to have slowed the purging. I believe the stop leak settled in the overflow tank and radiator was unable to retrieve coolant from tank.

Any advice on what the culprit is will be greatly appreciated. Next step is compression test...wish me luck.

 

Compression test for all cyl was between 170-180 psi. So maybe a valve problem??? When plugs were removed for comp check, they all seemed slightly 'wet'. not sure if it was oil or a fuel mixture of some type and didn't taste like coolant, or so i was told so i am not really sure where to go from here with the miss. I did notice that the chilton manual that i have indicates a gap of .045 however the sticker under the hood states .060 Plugs will be installed in accordance with the sticker unless i hear back from anyone stating otherwise. 'High' idle was determined to be from TBI vacuum leak (learned from old thread compliments of Mr. Shamrock) THANKS!!! So.... still need help on misfire and coolant leak issue...

Uploaded (i think) is a pic of the inside of the throttle body. doesn't look to clean to me...

 

How many miles are on the motor? How about the MAF sensor is the screen clean and undamaged?

 

That can result from a bad PCV. Just a suggestion.

 

I don't have my specs in front of me, but that compression seems good. So that should rule out a valve issue unless it's a valve seal allowing oil to foul out your plugs on those cylinders. Need to find out if it is oil or gas on the plugs. These motors are notorious for the spider injection leaking which could cause plug fouling. I think I would pull the valve covers and visually inspect the valve seals and oil passages/drains to make sure you don't have oil puddling in your heads. If they look OK I would pull the intake and check the "legs" on the spider injection. While your there obviously you will need to install new intake gaskets, which is another common issue on the Vortec motors and could be the cause of your high idle (vacuum leak) and could contribute to your coolant loss. Hope this helps!

 

I have replaced the PCV already and it didn't help. Truck has 138K miles. On my way to the parts store to pick up some gaskets for valve covers and intake. Will have pictures up by the end of the week and an update on valve seals and idle situation. Thanks again all!

 

Well a new PCV is not gonna yield instant results. Just make sure to change it very often my friend.

 

Will do with the PCV Ruff. Also, back to the issue with taking the oil cap off while the vehicle is running. I know it's not recommended to run your vehicle without one. But, if i remember correctly, when i change the oil in my pickup I will normally leave the oil cap off and run the engine for a few minutes to cycle the oil through the filter. Then, recheck the level to ensure full capacity. I was told by a mechanic shop that the engine will die if the oil cap is removed due to vacuum issues during normal operating conditions. I am not entirely sure if he is correct. Any reassurance on this issue?

 

When my dad had his oil changed at a dealership they forgot to replace the oil cap. My dad being a completely moronic old man forgot to check. He drove for two days without the cap on the engine. No ill effects in the way of the engine dieing. I'm sure however that there will be other downfalls to that happening.

 

WELL.............who ever told you it had to do with vacuum issues was WRONG!!!!! The crankcase has positive pressure...........hence the Positive Crankcase Ventilation valve...PCV...the biggest problem with running with no pcv is the POSSIBLE loss of oil and MAYBE some irratic idle.